Project Abstract Child neglect is the dominant referral problem among families entering the child welfare service system, comprising two-thirds of all entering cases nationally. Neglect cases are characterized by high recidivism, and relatively high negative impact on children with respect to health, mental health, and behavioral outcomes. Most neglect cases are served by in-home family preservation/family reunification (FP/FR) service systems. Many FP/FR services-as-usual are based on a loose social support and case management model, and more effective models with stronger scientific support, such as the SafeCare model, have not yet penetrated into FP/FR service systems. How to diffuse evidence-based models throughout these systems, and maintain sustained fidelity, is an open question. Results from two ongoing NIMH-funded studies of a statewide SafeCare controlled-trail implementation in Oklahoma have yielded initial findings that some implementation features (e.g. in vivo provider coaching) are critical. In this proposal, we will test a new and promising implementation and diffusion approach developed for transporting SafeCare into an existing FP/FR service network in San Diego County California. The proposed study will take advantage of a new, recently funded implementation project, scheduled to begin in September, 2007. The proposed study will use this already funded implementation as a vehicle for expanding scientific knowledge about the implementation and diffusion project. The diffusion model involves a cascading approach, first developing a small seed program of exceptionally high quality, then using providers from the seed program as in vivo coaches and implementation agents for sequential implementations at other provider agencies in the system. This study will examine whether or not the planned diffusion model can develop a network of services with self-sustaining levels of model fidelity and provider competency across cascading waves of individual agency implementation. Also, using a mixed-methods (quantitative/qualitative) approach, we will examine and describe the relationship between individual provider staff, system, and organizational factors, and their impact on the implementation process. The anticipated results of the study will be a rich data set systematically describing key factors and issues involved in diffusion of an EBT within a child welfare FP/FR service system along with data on the effectiveness of the diffusion model in achieving sustained model uptake.